1. Field of the Invention
This invention relates generally to alternative sources of energy using wind driven electricity generation and, more particularly to a system and method utilizing a Savonius type wind turbine rotor for generating electrical power from wind energy.
2. Background Art
Published prior art since 1924 encompasses the fundamental characteristics and physical behavior of the wing rotor invented by Sigurd J. Savonius. Savonius was granted British Patent GB 244414 in 1926, British Patent GB 299634 in 1928, and U.S. Pat. No. 1,766,765 in 1930. His original work (Savonius, S. J., “The Wing-Rotor in Theory and Practice,” Self published by Savonius & CO., Helsingfors, Finland, 39 pp., 1925) summarizes eight months of experiments with about 40 models of various sizes, forms and wing types. The original analysis, summarized in an article (Savonius, S. J., “The S-Rotor and its Applications,” Mechanical Engineering, vol. 53, no. 5, pp. 333-8, May 1931), provided an estimate of peak efficiency (31%), as well as loading and rotation properties, that is consistent with numerous subsequent studies. Primary emphasis of many of these studies was on measurements of power conversion efficiency and confirmation of rotor operating properties that had been articulated by the inventor Savonius.
The overwhelming international attention during the 20th century to inverse propeller driven horizontal axis wind turbines (HAWTs) has relegated the variants of the vertical axis Savonius rotor to academic curiosity. The lack of interest and incentive for applying the Savonius rotor to power generation of more than a few kilowatts is partly attributable to a historical accident wherein two efficiency curves were incorrectly labeled in a published article concerning the rotor which led to the misimpression that the rotor has relatively low efficiency.
Many alternatives and wind energy conversion applications have been suggested to increase rotor performance by means of vane configuration, external appurtenances, and other mechanisms. The following are some examples: Savonius, U.S. Pat. No. 1,766,765; Norton et al, U.S. Pat. No. 4,005,947; Peed, U.S. Pat. No. 4,061,926; Baum, Sr., et al U.S. Pat. No. 4,177,009; Benesh, U.S. Pat. Nos. 4,359,311; 4,784,568; 4,830,570; 4,838,757; and 5,494,407; Borg et al, U.S. Pat. No. 6,283,711; Szpur, U.S. Pat. No. 6,345,957; Kaneda, U.S. Pat. No. 7,220,107; Gabys, U.S. Pat. No. 7,352,076; and Rahai et al, U.S. Pat. No. 7,393,177.
Of these studies and patents related to wind generation of electric power, none have contemplated rotor rotation rates and a mechanism for energy conversion that are comparable to the present invention. Most of the Savonius rotor wind generation systems of the prior art utilize a generator coupled to a single central shaft. However, the much lower rotation rate of the Savonius rotor markedly increases mechanical problems of single shaft power generation.